1、BRITISH STANDARD BS 7457:1994 Specification for Polyurethane (PUR) foam systems suitable for stabilization and thermal insulation of cavity walls with masonry or concrete inner and outer leavesBS7457:1994 This British Standard, having been prepared under the direction of the Plastics and Rubber Stan
2、dards Policy Committee, was published under the authority of the Standards Board and comes into effect on 15 April1994 BSI 08-1999 First published September 1991 Second edition March 1994 The following BSI references relate to the work on this standard: Committee reference PRM/72 Draft for comment 9
3、2/45661 DC ISBN 0 580 22833 9 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Plastics and Rubber Standards Policy Committee (PRM/-) to Technical Committee PRM/72, upon which the following bodies were represented: Association of Building
4、 Component Manufacturers Brick Development Association British Board of Agrment British Plastics Federation British Rigid Urethane Foam Manufacturers Association Calcium Silicate Brick Association Limited Cavity Foam Bureau Department of the Environment (Building Research Establishment) Department o
5、f the Environment (Construction Industries Directorate) Engineering Equipment and Materials Users Association European Phenolic Foam Association Flat Roofing Contractors Advisory Board Ministry of Defence National Federation of Roofing Contractors National House-building Council Polyethylene Foam In
6、sulation Association Royal Institute of British Architects The following bodies were also represented in the drafting of the standard, through subcommittees and panels: British Ceramic Research Ltd. British Urethane Foam Contractors Association (BUFCA) RAPRA Technology Ltd. Amendments issued since p
7、ublication Amd. No. Date CommentsBS7457:1994 BSI 08-1999 i Contents Page Committees responsible Inside front cover Foreword ii Introduction 1 1 Scope 1 2 References 1 3 Definitions 1 4 Designation of polyurethane foam 2 5 Property requirements 2 6 Processing requirements 2 7 Marking 4 Annex A (infor
8、mative) Notes for designers 5 Annex B (normative) Method for the determination of masonry adhesion strength 5 Annex C (normative) Method for the determination of the polyurethane foam appearance 5 Annex D (normative) Method for the determination of effective density 6 Annex E (normative) Method for
9、the determination of the polyurethane foam system reaction profile 6 Table 1 Designation codes for thermal conductivity 2 Table 2 Property requirements: type tests 3 Table 3 Property requirements: quality control tests 3 Table 4 Permissible deviations on declared values for polyurethane foam system
10、components 4 List of references Inside back coverBS7457:1994 ii BSI 08-1999 Foreword This British Standard has been prepared under the direction of the Plastics and Rubber Standards Policy Committee. It supersedes BS7457:1991 which is withdrawn. This edition introduces technical changes but it does
11、not reflect a full review or revision of the standard. It is envisaged that this standard will be replaced by a European Standard in due course and that the European Standard will be adopted in the BSEN series. Requirements have been included for the thermal conductivity to be designated by the manu
12、facturer. The installation of suitable polyurethane foam into the cavities of masonry walls is widely recognized as providing an improvement in their thermal insulation. At the same time the high strength characteristic of the material and its good adhesion to masonry has led to its being widely ado
13、pted as an effective method for stabilizing walls in which the wall ties have, by corrosion, become inoperative. The successful installation of polyurethane foam into external cavity walls relies on two standards, i.e.this standard which specifies the requirements for the polyurethane foam systems,
14、and the code of practice, BS7456:1991, which gives recommendations designed to achieve the optimum installation of the polyurethane foam systems specified in this standard in masonry or concrete cavity walls. A British Standard does not purport to include all the necessary provisions of a contract.
15、Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 6, an inside back cover an
16、d a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS7457:1994 BSI 08-1999 1 Introduction A suitable polyurethane foam system may be injected into a masonry cavity wall
17、by injecting the liquid polyurethane foam system through properly spaced holes in the outer leaf. The polyurethane foam system expands in the cavity and sets to become a substantially closed-celled cross-linked rigid polyurethane foam which is strongly adhered to the inner and outer leaves, so that
18、these leaves become bonded together. Such a system comprises an isocyanate, a polyol (an isocyanate reactive resin usually containing two or more hydroxyl groups) and an expanding agent, which is a liquid at normal UK ambient temperatures and is usually incorporated as a liquid into the polyol compo
19、nent. Thus the operation consists on site of continuously mixing the two components correctly and inserting the resultant foam system into the cavity. The expansion results from the vaporization of the expanding agent due to the heat generated by reaction of the polyol and isocyanate. Because the st
20、rength of the rigid polyurethane foam is significant the system has been widely used for the restoration of the integrity of cavity walls in which the wall ties have become ineffective due to corrosion. The installed rigid polyurethane foam thus confers two benefits namely insulation and interleaf b
21、onding. It should be stressed that, while polyurethane foam is a satisfactory replacement for normal metal wall ties it does not prevent corrosion of existing ties in a wall nor halt the deterioration caused by such corrosion. All installations in walls to deal with corroding wall ties have to be ac
22、companied by a suitable treatment of the existing ties such as removal, isolation (see A.9 of BS7456:1991). 1 Scope This British Standard specifies the property requirements, composition, and the production parameters of suitable rigid polyurethane foam (PUR) systems, which are dispensed on site, to
23、 fill the cavities of maximum width150mm of suitably constructed external walls of maximum continuous cavity height12m which have masonry or concrete inner and outer leaves, thereby providing additional thermal insulation to such walls and simultaneously, especially in the case of damaged wall ties
24、improving their structural integrity. 2 References 2.1 Normative references This British Standard incorporates, by dated or undated reference, provisions from other publications. These normative references are made at the appropriate places in the text and the cited publications are listed on the in
25、side back cover. For dated references, only the edition cited applies; any subsequent amendments to or revisions of the cited publication apply to this British Standard only when incorporated in the reference by amendment or revision. For undated references, the latest edition of the cited publicati
26、on applies, together with any amendments. 2.2 Informative reference This British Standard refers to another publication that provides guidance. The edition of this publication current at the time of issue of this standard is given on the inside back cover, but reference should be made to the latest
27、edition. 3 Definitions For the purposes of this British Standard the following definitions apply. 3.1 polyurethane foam the cellular polymer resulting from the reaction of the two components of the foam system, i.e the isocyanate and polyol components 3.2 polyurethane foam system a mixture of polyol
28、 component and isocyanate component which is to be injected into the cavity wall 3.3 isocyanate component a liquid isocyanate material which when mixed with the polyol component comprises the foam system 3.4 polyol component a liquid polyhydroxyl compound containing an expanding agent, catalysts and
29、 other additives which when mixed with the isocyanate component comprises the foam system 3.5 cavity an air space between two leaves of an external wall 3.6 effective density the mass of a specified sample divided by its initial volume using the method described in Annex DBS7457:1994 2 BSI 08-1999 3
30、.7 declaration the document supplied by the polyurethane foam system supplier to the purchaser or to any authorized testing or approvals organization, containing relevant details for the proper use of the foam system 3.8 end of rise time the time taken after the polyurethane foam system (3.2) has be
31、en mixed for the foam expansion to be visibly completed 3.9 cream time the time taken after the polyurethane foam system (3.2) has been mixed for visible expansion to commence 3.10 tack free time the time taken after the polyurethane foam system(3.2) has been mixed for the surface of the expanded po
32、lyurethane foam not to adhere to the test stick (seeE.2.4) 4 Designation of polyurethane foam The foams shall be designated to indicate their thermal conductivity (see5.3). The designation shall consist of a two component code comprising the following items in the order presented: a) the number and
33、date of this British Standard; b) a double digit number to indicate the thermal conductivity selected in accordance with Table 1. An example of the designation of foam with a thermal conductivity of0.020W/(mK) is as follows: BS 7457:1994/20 5 Property requirements NOTEThe quality of the polyurethane
34、 foam depends upon the choice of raw materials and their method of use as declared by the polyurethane foam system supplier. 5.1 Type tests The polyurethane foam system (3.2) shall produce polyurethane foam (3.1) which shall meet the property requirements given in Table 2 when prepared in accordance
35、 with the foam system suppliers declaration (see 6.2) and dispensed into a cavity of the appropriate thickness between materials covered by the scope of this specification. 5.2 Quality control tests NOTEDetails of when these tests are to be carried out are given in 7.4 of BS 7456:1991. The appearanc
36、e, effective density and reaction profile of the polyurethane foam shall be as given in Table 3. 5.3 Thermal conductivity Thermal conductivity shall be determined by either method 7A or 7B of BS4370-2:1993 at a mean temperature of10 C, (30 2) days after manufacture. Materials shall be conditioned th
37、roughout this period at (23 2) C and (50 5)% r.h. NOTESee additional guidance in Annex A concerning the thermal conductivity 3 day values and design value. Table 1 Designation codes for thermal conductivity 6 Processing requirements 6.1 Polyurethane foam system components The application technique o
38、f the two polyurethane foam system components (3.3 and 3.4) shall be as declared by the polyurethane foam system supplier, including any storage requirements. The values of the properties given in Table 4 for the system components shall be declared for each foam system by the system supplier. The co
39、mponent property values shall then conform to the permissible deviations given in Table 4 and associated declared values. Thermal conductivity (see 5.3) Code W/(mK) 0.015 0.016 0.017 0.018 0.019 0.020 0.021 0.022 0.023 0.024 0.025 0.026 0.027 0.028 0.029 0.030 0.031 0.032 15 16 17 18 19 20 21 22 23
40、24 25 26 27 28 29 30 31 32 NOTEThese values are30day values for quality control purposes. For corresponding long term design values the manufacturers advice should be sought (seeAnnex A).BS7457:1994 BSI 08-1999 3 Table 2 Property requirements: type tests Table 3 Property requirements: quality contro
41、l tests Physical property Test requirement Test method Minimum compressive strength normal to the major plane of the cavity, kPa Method 3 of BS 4370-1:1988 130 On foam from a cavity 50 mm to 100 mm thick 115 On foam from a cavity 100 mm to 150 mm thick Minimum shear strength parallel to the major pl
42、ane of the cavity, kPa Method 6 of BS 4370-2:1993 100 On foam from a cavity 50 mm to 100 mm thick 90 On foam from a cavity 100 mm to 150 mm thick Dimensional stability maximum mean linear change,% Method 5A of BS 4370-1:1988 Test conditions Cut the length and width of the test specimen parallel to t
43、he major plane of the cavity 24 h at ( 15 2) C 1 24 h at (100 2) C 2 Maximum water vapour permeability parallel to the foam thickness, ng/(Pasm) Method 8 of BS 4370-2:1993 Condition a) 7 Carry out the test at (38 0.5) C and (88 2)% r.h. on one face of the test specimen and 0% r.h. on the other. Cut
44、the cylindrical test specimens (25 5) mm thick such that their plane faces are parallel to the major plane of the foam Minimum closed cell content, apparent volume% 85 Method 10 of BS 4370-2:1993 Burning characteristics amaximum extent of burning, mm 125 BS 4735:1974 Minimum masonry tensile adhesion
45、 strength, in kPa, measured for Annex B a) aerated concrete; 50 On a foam thickness of 50 mm to 100 mm thick b) brick; 30 b On a foam thickness of 100 mm to 150 mm thick c) breeze block a CAUTION. The small scale laboratory test described in BS4735:1974 is solely for assistance in monitoring consist
46、ency of production and is not for use as a means of assessing the potential fire hazard of a material in use. b Manufacturers often offer systems giving values considerably higher than this value. Property Test requirement and permissible deviations Test method Appearance Uniform, fine, cellular str
47、ucture Annex C Effective density, kg/m 3 Target value to be specified by the polyurethane foam systems supplier see 6.2 c) Annex D Reaction profile, s To be specified by the polyurethane foam systems supplier see 6.2 c) Annex EBS7457:1994 4 BSI 08-1999 Table 4 Permissible deviations on declared valu
48、es for polyurethane foam system components 6.2 Declaration The polyurethane foam system supplier shall make a declaration (3.7) for each polyurethane foam system with respect to the following parameters: a) the required ratio of the components; b) any storage limitations; c) the data required in Tab
49、le 3 and the values of the properties given in Table 4; d) the health and safety requirements 1) . 7 Marking The containers or invoice shall be marked with at least the following information: a) manufacturers name or trademark; b) product designation as given in clause 4; c) manufacturers description and/or product reference. NOTEMarking BS7457:1994 on or in relation to a product represents a manufacturers declaration of conformity, i.e.a claim by or on behalf of the manufacturer that the product meets the requirements of th
